1. Field of the Invention
The present invention relates to a package structure, and more particularly to a backlight module and a light emitting diode (LED) package structure thereof.
2. Description of Related Art
In recent years, since luminescence efficiency of LEDs has been constantly upgraded, fluorescent lamps and incandescent bulbs are gradually replaced with the LEDs in some fields, such as a scanning light source which requires high reaction speed, a backlight source of a liquid crystal display (LCD), car instrument panel illumination, traffic signs and general illumination devices.
The LEDs is point light sources. Thus, as the LEDs are applied to the backlight sources of the LCDs, the LEDs are arranged in array in most cases, and light beams provided by the backlight sources are uniformly mixed before the light beams are transmitted to LCD panels, so as to provide planar light sources emitting uniformly-mixed white light beams for the LCD panels. Here, as the LEDs are applied to edge-type backlight modules, a Lambertian LED package structure 100a (shown in FIGS. 1A and 1B) characterized by converged light beams or a batwing LED package structure 100b (shown in FIGS. 2A and 2B) is usually adopted.
Taking the backlight source composed of one or more Lambertian LED package structures 100a adapted to emit red lights, green lights or blue lights for an example, when a pitch among each of the LED package structures 100a is 9 mm, the light beams provided by the LED package structures 100a require a 28-mm light-mixing distance for mixing the light beams into the uniform white light beams. However, since the pitch among each of the LED package structures 100a is almost unlikely to be shortened by virtue of the volume of the LED package structures 100a, the light-mixing distance thereof is not likely to be shortened as well. Accordingly, the volume of the backlight module cannot be reduced.
In order to reduce the light-mixing distance of the light beams provided by the LED package structures 100a, an LED package structure 100c (shown in FIGS. 3A and 3B) having three chips is proposed by the related art. The LED package structure 100c has a red LED chip 110r, a green LED chip 110g, and a blue LED chip 110b. The LED chips 110r, 110g, and 110b are disposed in the same chamber 120. Thus, the light beams provided by the LED chips 110r, 110g, and 110b can be mixed in the chamber 120 at first and then projected out of the LED package structure 100c. As such, the light beams supplied by the LED package structure 100c have a relatively short light-mixing distance than the backlight source constituted by the LED package structures 100a does. Here, said light-mixing distance is 18 mm.
It should be noted that the square-shaped chamber 120 of the LED package structure 100c cannot achieve a converged effect, and hence the light beams provided by the LED package structure 100c may have a relatively short transmitting distance. Moreover, the degree of the luminance of the planar light source is larger nearby a light incident surface of a light guide plate (not shown) than away from the light incident surface thereof. Accordingly, as the LED package structure 100c is employed together with a large-sized light guide plate, unfavorable light uniformity may be achieved in an edge area of the planar light source emitted from a light emitting surface of the light guide plate.